Ajax.NET debugging
Most people use alert() to debug their JavaScript, but the Microsoft Ajax Library has a better alterative Sys.Debug. Sys.Debug has some methods for logging messages to the browser console. Like this:
To log a message:
Sys.Debug.trace(“Log to the console”)
To log an object:
Sys.Debug.traceDump(someObject);
You can use Web Development Helper for IE, and Firebug for Firefox to see your console messages. Or use textarea element with the id "TraceConsole" to trace your messages:
<textarea id=”TraceConsole” rows=”50” cols=”50”></textarea>
From:
http://weblogs.asp.net/alnurismail/archive/2009/01/12/a-better-alternative-to-using-alert-for-debugging.aspx